In motor vehicle security systems, it is advantageous to have the system regulate the operation of the vehicle's engine in order that the engine operates only if an authorized operator is confirmed to be present. One type of security system, a motor vehicle engine immobilizer system, offers this security by preventing the motor vehicle engine from operating fully unless a valid, electronically-coded, ignition key is provided in the vehicle's ignition lock. Whenever an ignition request is made, the electronics system that governs engine operation checks to make sure a valid ignition key is provided in the vehicle ignition, either through direct communication with the coded ignition key or direct communication with an intermediate theft deterrent module. This process of checking for ignition key validity is referred to throughout the document as the “authentication process.” If a valid ignition key is inserted in the ignition, the engine electronics system allows the engine to start and run. If a valid ignition key is not present in the vehicle ignition, the engine electronics system disables engine starting and prevents any further use of the engine until a valid ignition key is provided in the vehicle ignition.
Complex encryption mechanisms are often used by engine immobilizer systems to ensure adequate security for the entire authentication chain, from ignition key to engine management system. Using these complex mechanisms prevent unauthorized users from manipulating the vehicle's electronics system into thinking that a valid ignition key is present in the vehicle ignition. The downside of using such complex mechanisms is that it often takes longer for the vehicle's electronics system to process these codes in order to determine whether or not a user is authorized to use the vehicle. As it is undesirable to have a noticeable pause from the time an ignition key is turned to the “start” position in a vehicle ignition until the time when the vehicle engine actually begins to turn over and start, engine immobilizer systems sometimes allow the vehicle engine to start prior to full user authentication. Allowing the engine to start before completion of the authentication process thus avoids the unwanted time delay. The time period during which the engine is allowed to run, but before user authentication is complete, is known as a “pre-authorization engine operation time.” To optimize engine operational requirements, such as those relating to emissions and engine durability, this pre-authorization engine operation time should be set fairly long; but, in the interest of security, to make the engine immobilizer system less prone to security breaches by unauthorized users, it is advantageous to set this time fairly short.
Accordingly, it is desirable to provide a motor vehicle theft deterrent engine immobilizer apparatus and method that prevents an unauthorized entity from operating a motor vehicle but that does so with a high degree of security and without an undue delay in vehicle starting by an authorized user. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.